Conventional Complementary Metal Oxide Semiconductor (CMOS) devices have been the primary electronic technology for over half a century. However, continuous scaling of conventional CMOS devices has resulted in challenges to reduce power dissipation and to lower variability. Spintronics, with its unique properties of magnetism in metallic and semiconductor nanostructures, has emerged as a possible technology for meeting these challenges.
Spintronic devices, namely spin transistors, operate based on the propagation of the spins of electrons rather than the transport of the charge of the electrons. More specifically, it has been shown that when current flows through a ferromagnetic layer into an ordinary metal, electrons retain their original spin polarization and, therefore, the polarized spin along a magnetic field can be transported just like charges. This concept has resulted in several attempts to fabricate spin transistors that exploit the spin dependent transport of charge carriers in order to yield a device with high spin current gain and high magnetic sensitivity. One such area of research is electric field control of ferromagnetism of Dilute Magnetic Semiconductors (DMSs).
Electric field control of ferromagnetism of DMS has the potential to realize spin Field Effect Transistors (s-FETs) and nonvolatile spin logic devices via carrier mediation. In general, the magnetic states of DMS materials could be controlled by an external electric field, in which the carrier density inside the DMS materials is altered. It has been observed that this transition from the paramagnetic to ferromagnetic state is a result of the accumulation of carriers (e.g., holes) in the DMS material in response to the application of the appropriate electric field much in the same manner as an accumulation mode of a Metal-Oxide-Semiconductor (MOS) capacitor. More specifically, the carriers interact with magnetic ions in the DMS material in such a manner that the DMS material transitions from its normal paramagnetic state to the ferromagnetic state when a large number of carriers are accumulated in the DMS material, and vice versa. This is referred to as the “carrier-mediated effect.” However, spin transistors that operate based on the carrier-mediated effect, which are referred to herein as carrier-mediated paramagnetic-ferromagnetic (PF) s-FETs, are difficult to achieve for room temperature applications because of the challenges in obtaining, among other things, carrier induced ferromagnetism at room temperature.
Thus, there is a need for a carrier-mediated PF spin transistor for room temperature applications.